Machine-switching telephone-exchange system



Dec. 9, 24- 1,518,815

L. POLINKOWS KY MACHINE SWITCHING TELEPHONE EXCHANGE SYSTEM Filed Dec.28. 1918 '7 Sheets-Sheet 1 Dec. 9, 1 24. 1,518,815

L. POLINKOWSKY MACHINE SWITCHING TELEPHONE EXCHANGE SYSTEM //7 ven for.

L/pa Po/fn/rows/(y i Dec. 9, 1924- L. POLINKOWSKY MACHINE SWITCHINGTELEPHONE E/XCIQAN'GE SYSTEM Filed De 28. 1918 '7' Sheets-Sheet 5"//7-V6/7/0/.' Lf va Po/mkawsky Affjc 1,518,815 L. POLINKOWSKY MACHINESWITCHING TELEPHONE EXCH ANGE SYSTEM Fil d 80- 28. 1918 '7 Sheets-Sheet4 //1 1/01 for L/pa Po/f/vkows/ry.

by A/fy Dec. 9, 1924. 1,518,815

LI POLINKOWSKY MACHINE SWITCHING TELEPHONE EXCHANQE SYSTEM E I i 507 2F5,". 1 .575 5.72 53/ l: 2n,

v F a z .584 y //7 van fan Lip Po/fn/mwsky.

L. POLlNKOWSKY MACHINE SWITCHING TELEPHONE EXCHANGE SYSTEM //7 V6/7far." L 24; Po/flv/mwsky Dec. 9, 19.24. 1,518,815

L. POLINKOWSKY MACHINE SWITCHING TELEPHONE EXCHANGE SYSTEM Filed Dec.28. 1918 7 Sheets-Sheet 7 F 45.7 T] 3 1. a T4 5;

v 447 IZtol g M 44/ -442 44a //1ve'nf0r.'

L40 Po/fn/rowsky y W Afffy.

Patented Dec. 9, 1924.

UNITED STATES PATENT OFFICE.

LIPA POLINKOWSKY, 0F HYDE PARK, LONDON, ENGLAND, ASSIGNOR T0 WESTERNELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEWYORK.

MACHINE-SWITCHING TELEPHONE-EXCHANGE SYSTEM.

Application filed December 28, 1918. Serial No. 268,649.

To all whom it may concern:

Be it known that I, LIPA PoLINKoWsKY,

a citizen of Russia, residing at 70 Westbourne Terrace, Hyde Park,London, W1, England, have invented certain new and useful Improvementsin Machine-Switching Telephone-Exchange Systems, of which the followingis a full, clear, concise, and exact description.

This invention relates to machineswitching telephone exchange systemsand more particularly to a telephone exchange system in which calls maybe extended between a plurality of exchanges in the system.

A feature of the invention is the provision of means for the automaticadvance of a group selector from one stage to another in the progress ofthe establishment of a connection, if the group selector remains at saidstage in its sequence of operations longer than a predetermined lengthof time.

Another feature of the invention and one relating to the first named.feature is the provision of means, associated with the selectors used inextending a call, and in which a preceding selector of a chain ofselectors is controlled in its advance from one stage to another by thesucceeding selector, whereby the advance of the preceding selector fromsaid stage takes place automatically if the succeeding selector fails toact within a predetermined length of time.

In telephone exchange systems in which a call is extended over atwo-wire trunk line to selectors in a distant exchange and in which afundamental. circuit becomes extended metallically, free of bridges,etc., to

the chain of selectors in succession,-a preceding selector is broughtinto condition by the succeeding selector to be controlled from theoutgoing end of the trunk line after the completion of the selection.

A further featu e of the invention, therefore, is the provision of meansto advance a preceding selector of a chain of selectors into a stage tobe controlled from the outgoing end of a trunk line if the advance of a'succeeding. selector is prevented for a given length oftime. I

A still further feature of the invention and one relating to the lastnamed feature is the provision of means associated with a dead levelcircuit to advance a selector on the incoming end of a trunk line fromone stage to another if the selector remains at said first stage longerthan a predetermined length of time.

A still further feature of the invention and one relating to the secondlast named feature is the provision of means associated with theselectors at the distant exchange whereby the selectors will beprevented from being placed under the control of the outgoing end of atrunk line if the call is not extended because of the trunk hunting orrepeated trunk hunting operation of a selector.

A further feature of the invention is the provision of means under thesimultaneous and independent control of a succeeding selector and acommon timing arrangement for the advance of a preceding selector fromone stage to another.

A further feature of the invention is the provision, in telephoneexchange systems in which the outgoing end of each of a group oftwo-wire trunk lines is provided with circuits and apparatus formaintaining the trunk line busy until the incoming end thereof is free,of means including common conductor for rendering the engaged trunk idleresponsive to the release of the incoming end of the trunk.

In the drawings.

Fig. 1 shows a subscribers line and a first line finder.

Fig. 2 shows a cord circuit comprising a second line finder and a firstgroup selector.

Figs. 3 and 4: show a register equipment.

In Fig. 5 is shown a second group selector on the incoming end of atwo-wire trunk line, and in Fig. 6 a third group selector.

Fig. 7 shows a final selector.

Fig. 8 shows a common arrangement which controls the release of secondgroup selectors on two-wire trunk lines.

In Fig. 9 is shown a dead level circuit.

Fig. 10 shows an arrangement for increasing the time interval of themechanism illustrated in Fig. 8.

The system disclosed as embodied in the present invention will be bestunderstood from a description of the operation thereof.

\Vhen the line relay 201, in Fig. 1, is energized, the common. startingrelays 204 provide a circuit for the energization of the power magnets211 of the free firstline finders in the group. The brush carriages ofthese line finders rotate and in reaching terminal 210 of the callingline, test relay 214 of a line finder is energized and the terminal 210is made busy through the connection of the low resistance winding ofrelay 214 and the winding of relay 212 in parallel to the highresistance winding of relay 214. Relay 212 disconnects the power magnet211 and provides a circuit, for the energization of the holding magnet215 and the common starting relays 216. The brush carriage is arrested,and a circuit is provided for the free second line finders which haveaccess to this first line finder. Thesecond line finders, are dividedinto pairs and their sequence switches 220 are held either in position18 or position 1. Only the line finder of a cord, on which the sequenceswitch 220 is in position 1, is able to search for a calling first linefinder. Relay 222 of the cord is a then energized in a circuit over thefront contacts of the common starting relays 216. The power magnet 221is energized in a circuit from battery, through lower contact 290, thewinding of power magnet 221, back contact and armature of relay 232,front contact and armature of relay 222 to ground at; the back contactand armature of relay 231 and the brush carriage of the second linefinder rotates. On reaching terminal 230 the test relays 234 and 232 areenergized, terminal 230 is made busy and sequence switch 220 isenergized in a circuit over front contact of relay 232. Sequence switch220 starts from position 1 and moves into position 4. In position 3 ofsequence switch 220 a circuit is established for the energization ofrelays 235 of the cord, relay 213 of the first line finder and cut-olfrelay 207 of the calling line, whereby relay 201 is de-energized and thebrush carriages of the remaining free first and second line finders arearrested. The release relay 231 together with retardation coil' 237 isbrought into connection with the calling line.

In position 4 of sequence switch 220 the searching. sequence switch 280of the cord is energized and a free register set is searched. Thecircuit for sequence switch 280 may be traced from battery through thewinding of said sequence switch, upper-contact 291, back contact andarmature of relay 232, upper contact 281 to ground at lower contact 282.Assuming the register set in Figs. 3 and 4 free, a connection with this@1'egister set is obtained as soon as sequence switch 280 reachesposition 1 or 7. Relays 234 and 232 are thereby energizedin a circuitover conductor 293, contact 322 of sequence switch 320 and right handwinding of relay 323. Sequence switch 280 is arrested and sequenceswitch 220 is advanced into position 5. The calling subscribers line isbrought into connection with the secondary windings of the dialling tonecoil 324 and the stepping relay 325 of the register set, the circuitincluding the back contacts of key 301 at the monitoring position. Relay323 when energized provides over its front contact its'left hand windingand contact 326 bottom a circuit for the energization of sequence switch320, which controls the steppingin circuit and connects the registers insuccession with the contact of the steppingin relay 325. Sequence switch320 starts from position 1 and moves into position 3. In positions 2'and 3 of this sequence switch the primary winding of the dialling tonecoil 324 is connected over sequence switch contact 332 in a circuit witha common interrupter 333 and the calling subscriber,-

when receiving the sharp dialling tone, winds up the dial to send thefirst figure of the wanted number. When both contacts 322 and 326 ofsequence switch 320 are opened, relay 323 is d'e-energized. The tenthousands register 100 is energized in a circuit over sequence switchcontact 328 top-,

lay 329 remains energized until the line circuit is opened at the dialand relay 325" is d'e-energized. Relay 329' in closing its back contactagain prepares the circuit for register 100 which receives current assoon as relay 325 is again energized. Over the back contact of relay329,. the relay 337 is connected in parallel tothe register, and therelay 337, when energized provides over its front contact a shunt aroundthe front contact of relay 325. Relay 337 remains energized until theregister reaches itsnext position and its local contact is opened. Onthelast interruption at the dial relay 325 remains ole-energized for acomparatively long time and the slow operating relay 334 is energized ina circuit over back contactsof relays 325 and 323 and sequence switchcontact 342 top. Relay 323 is then energizedin a circuit over the frontcontact of relay 334. Sequence switch 320 is again energized, startsfrom position 3 and moves into position 6. Relay 325 is energized overthe calling line before sequence switch 320 reaches position 5. The tenthousands register is disconnected and the circuit is prepared forthethousands register 110 over sequence switch contact 328 bottom,contact 326 bottom being opened when the sequence" Register switch ismoving from position 3 to position 4 after contact 328 bottom is closed.The first energization of register 110 takes place immediately the backcontact of relay 323 is closed. Register 110starts from position 0 andin closing its contact 111, the right hand winding of relay 329 isshortcircuited and relay 329 opens its back contact, and the registercompletes its step under the control of its contact 111 and is arrestedin position 1. Relay 337 is new connected in parallel to register 110and maintains the energiz'ation of relay-329 during the time contact 111is closed. When the dial is released a second time register 110 isbrought to a corresponding 3081111011 and sequence switch 320 is advancefrom position 6 into position 8 in which the thousands register isdisconnected and the hundreds register 120 is now connected in thestepping circuit over sequence switch contact 335, and is set upaccording to the third series of impulses from the dial. Sequence switch320 is then advanced from position 8 into position 11 in which the tensregister 130 is connected in the stepping circuit over sequence switchcontact 336 top, after which sequence switch 320 is advanced fromposition 11 into position 13 in which the units register 140 isconnected in the stepping circuit over sequence switch contact 336bottom. WVhen the dialling is completed sequence switch 320 is advancedinto position 15.

The capacity of the exchange is assumed to be 100,000 lines. First,second and third group selectors and final selectors are thereforeprovided. The position of the registers determines the translation fromthe decimal number system of the wanted subscriber line to the system ofthe switches. The setting up of the selectors takes place during thetime the subscriber continues the dialling, and the operation of thetrip spindle of the first group selector is delayed until the firstimpulse series is completed on the dial. This corresponds to sequenceswitch 320 reaching position 4 in which a circuit is closed for theenergization of sequence switch 350 over contact'352 bottom and contact338 top of sequence switch 320. Sequence switch 350, which controls theconnection of the registers in succession for the setting up of theselectors, starts from position 1 and moves into position 3. The lefthand winding of relay 359 is energized in a circuit over back contact ofstepping-out relay 355 and contact 343 bottom of sequence switch 320.reaches position 3 the fundamental circuit is closed over contact 356top of sequence switch 350, back contact of relay 357, winding ofstepping-out relay 355, common wire 296 and winding of relay 222 at thecord. Both relays 222 and 355 are energized, relay When sequence switch350 359 is de-cnergized. Sequence switch 220 starts from position 5 andmoves into position 6 in which the trip spindle magnet 248 is energized.The trip spindlerotates and produces at its contact 250 topshort-circuitings around the winding of relay 355. As soon as the backcontact of relay 355 is closed the register 100 is energized in acircuit over contact 102, contact 364 top of sequence switch 350, backcontact and right hand winding of relay 359, contact 343 of sequenceswitch 320 and back contact of relay 355. Simultaneously with theenergization of register 100 relay 362 is'also energized and providesover its front contact a bridge to the contact of relay 355. Relay 362in the circuit for the outgoing impulses has the same purpose as relay337 in the circuit of the incoming impulses and enables a safe operationof the registers. Register 100 starts and closes its contact 101. Theright hand winding of relay 359 is short-circuited so that this relaybecomes energized, and the register completes its step under the controlof contact 101, after which relay 362 is de-energized. In the meantimetrip spindle contact 250 has been opened. The stepping relay 355 leavesits back contact, relay 359 is de-energized. On the following closure ofcontact 250 relay 355 isagain deenergized and register 100 is energized.When, under the control of relay 355, register 100 reaches position 0relay 357 and sequence switch 350 are energized on the followingde-energization of relay 355 in a circuit over sequence switch contact363 bottom, contact 104- of register 100 and contact 364 of sequenceswitch 350. Relay 35'? opens the fundamental circuit. Sequence switch350 starts from position 3 and moves under the control of its localcontact 351 into position 4.

When contact 351 is closed and the right hand winding of relay 359 isshort-circuited, this relay maintains its energization over back contactof relay 355. After contact 250 of the trip spindle is opened relay 222is deenergized. Sequence switch 220 starts from position 6 and movesinto position 7 in which the test relay 234 is connected to the testbrush 252 of the first group selector. Relay 222 is now energized in acircuit over conductor 293, contact 340 top of sequence switch 320 andback contact of relay 339. The power magnet 241 of the group selector isenergized in a circuit over front contact of relay 222. The brushcarriage rotates in the well known manner with the brushes along theterminal row determined by the position of the trip spindle. In reachingthe test terminal of a tree trunk line, relay 234 is energized in acircuit over test brush 252, resistance 500 and back contact of relay501. In parallel to resistance 500 the relays 501 and 502 are alsoconnected. Relay 234 of the cord brings its low resistance winding andthe Winding of relay 232 in parallel to its high resistance winding andmakes the terminal of the trunk line busy. Relay 232 is therebyenergized, power magnet 241 is disconnected and sequence switch 220 andthe holding magnet 245 of the first group selector are energized, thebrush carriage is arrested, and sequence switch 220 starts from position7 and moves over position 8 into position 9 in which the fundamentalcircuit is prepared at sequence switch contacts 247 top and 255 bottomto the second group selector pending the closure of the circuit at theregister set. Relay 502 when energized maintains at its left hand frontcontact the closure of the circuit over the test brush 252 independentfrom the left hand back contact of relay 501. Relay 501 provides for itsright hand winding a circuit over its left hand front contact and backcontact of relay 503. 1

Sequence switch 350 at the register set remains in position 4 until thesecond series of impulses at the dial has been completed and sequenceswitch 320 has left position 6. A circuit is then established for theenergization of sequence switch 350 over contact 354 and contact 338bottom of sequence switch 320. Sequence switch 350 starts from position4 and moves into position 6. The fundamental circuit is closed at theregister set over contact 358 bottom of sequence switch 350, backcontact of relay 378 and common wire 297. In the distant exchange thesequence switch 520 ofthe second group Selector on the incoming end ofthe two-wire trunk line is in its position of rest and relay 522 isconnected over sequence switch contact 504 top withconductor 536, whilerelease relay 523 together with retardation coil 524 are connected withthe second wire 537 ,of the trunk line over contacts 505 bottom and 506bottom of the sequence switch. The high resistance winding of relay 523prevents theenergization of relay 355 in the registerset. Belay523 isenergized andprovides a circuit for the energization of se quence switch520 overcontact 507 top and frontcontact of relay 523. Sequence switch520 starts from position 1 .and moves under the controlof its localcontact 521 into position 2,in whichrelay 522 is connected to wire 53.7over sequence switch contact 505 top, while wire 536 of the trunk lineis connected over sequence switch contact 508 with ground. Relays 522and 355 areenergized. Belay-359 is de-energized. The magnet 528 of thetrip spindle is energized in a circuit over sequence switch contact 509top and front contact of relay 522. The trip spindle rotates andprovides at its contact 510 v,top over sequence switch contact 511bottom short-circuitings .around the winding of relay 355. Assumingregister .11 having bee arrested in position 8, this register isenergized in a circuit over left. hand back contact of relay 360,contact 112 of register 110 and contact 361 top of sequence switch 350.After register 110 is brought to position 0 under the control of relay355, relay 357 and sequence switch 350 are energized on the followingde-energization of relay 355 in a circuit over contact 363 bottom ofsequence switch 350, contact 104 of register 100, contact 364 bottomofsequence switch 350, contact 114 of register 110 and Contact 3610fsequence switch 350. The fundamental circuit is opened at the backcontact of relay 357 while sequence switch 350 starts from position 6and moves into position 7.

As soon as contact 510 of the trip spindle is also opened relay 522 isde-energized and sequence switch 520 is energized .in a circuit overcontact 514 top and back contact of re lay 522. Sequence switch 520starts from position 2 and moves into position 3. Relay 522 is energizedin a circuit over sequence switch contact 511 top and contact 510 bottomof the trip spindle. The set of trip spindle interrupting contacts 510of switches of this character is so'arranged that all three contacts areopened when the trip spindle is standing in its normal position and suchthat the upper and middle contacts are opened and the lower and middlecontacts in engagement with each other when the trip spindle is moved toany of its brush tripping positions. To accomplish this end thelowermost contact is designed to engage a series of notches in therotating element of the trip spindle. The notch corresponding to thenormal position of the trip spindle is sufliciently deep to permit allthree of the contacts to remain open. The notches corresponding to thebrush trip positions, however, are more shallow in depth, whereby thelowermost contact is held in engagement with the middle contact, butthese notches are not sufliciently deep to press the middle contactintoengagement with the uppercontact. As the trip spindle rotates fromone position to another, the lower contact rides over the surface oftheteeth formed between the notches andall three contacts are closed. Theleft hand high resistance winding of relay 534 is now connected with thetest brush 512 over sequence switch contact 513 bottom, while the power,magnet 531 of the brush carriage isenergized in a circuit over sequenceswitch contact 515 bottom and back contactof second test relay 532. Thebrush carriage of the second group selector ,rotates searching for aterminal of a free third selector in the reaching of which relay 5 34 isenergized in a circuit over vtest brush .512,- contacts 567 and 541ofsequence switch 550 individual to this third group selector andresistance 542. In parallel to resistance 542 is also connected the highresistance ,winding of relay 543. Relay 534 brings over its frontcontact its right hand low resistance winding and winding of relay 532into connection with brush 512 and makes the test terminal to the thirdgroup selector busy. Relay 532 is energized, disconnects at its backcontact the power magnet 531 and provides a circuit for the energizationof sequence switch 520 over contact 507 bottom and front contact ofrelay 532. In parallel to sequence switch 520 the holding magnet 535 isconnected over its contact 516 bottom. The brush carriage is arrested,and sequence switch 520 starts from position 3 and moves into position 6in which terminal 512 is now connected over sequence switch contact 513top direct with relay 532, providing thereby a short circuit around theright hand winding of relay 534 which is thereby de-energized. Inposition 6 of sequence switch 520 the fundamental circuit is extendedover se quence switch contacts 517 and 518 to relay 552 of the thirdgroup selector.

Relay 543 when energized provides over its left hand front contact aholding circuit for its winding independent from contact 567 of sequenceswitch 550. A circuit is closed for the energization of sequence switch550 over contact 544 bottom and right hand front contact of relay 543.Sequence switch 550 starts from position 1 and moves into position 2.

Sequence switch 350 remains in position 7 until the third series ofimpulses is completed at the subscribers dial and sequence switch 320leaves position 8. A circuit is then established for the energization ofsequence switch 350 over contact 370 bottom and contact 341 top ofsequence switch 320. Sequence switch 350 starts from position 7 andmoves into position 9 in which the fundamental circuit is again closedat contact 358 bottom of sequence switch 350. Relay 552 of the thirdgroup selector and relay 355 of the register set are energized and relay359 is de-energized. Sequence switch 550 is energized in a circuit overcontact 549 top and front contact of relay 552. Sequence switch 550starts from position 2 and moves over position 4 into position 5. Themagnet 548 of the trip spindle is now energized in a circuit oversequence switch contact 553 top and front contact of relay 552. The tripspindle rotates and provides at contact 555 top bottom short-circuitingsaround relay 355. Assuming register 120 to have been arrested in an evenposition, the register is now restored to its position of rest under thecon trol of relay 355 in a circuit over contact 122 of register 120,contact 366 bottom of sequence switch 350 and back contact of relay 359.lVhen't-he register 120 reaches position 0 relay 357 and sequence switch350 are energized on the following de-energizaand over sequence switchcontact 556,

tion of relay 355 in a circuit over sequence switch contact 366, contact124 of register 120, sequence switch contact 361 bottom, contact 114 ofregister 110, sequence switch contact 364 bottom, contact 104 ofregister 100 and sequence switch contact 363 bottom. The fundamentalcircuit is opened, sequence switch 350 starts from position 9 and movesinto position 10.

lVhen contact 555 at the trip spindle is opened relay 552 isde-energized and sequence switch 550 is energized in a circuit overcontact 549 bottom and back contact of relay 522. Sequence switch 550starts from position 5 and moves into position 6 in which relay 552 isenergized in a circuit over contact 556 top of sequence switch 550 andcontact 555 bottom of the trip spindle, due to the construction of thetrip spindle contacts already explained in connection with the precedingswitch. The right hand high resistance winding of test relay 564 isconnected over sequence switch contact 546 top with the test brush 572.The power magnet 561 of the brush carriage is energized in a circuitover sequence switch contact 547 bottom and back contact of relay 562.The brush carriage of the third group selector rotates with the brushesin the row determined by the position of the trip spindle and onreaching the terminal of a free final selector, the right hand windingof relay 564 is energized in a circuit over brush 572, contacts 440 and441 of sequence switch 450 individual to the final selector andresistance 442. In parallel to resistance 442 .the high resistancewinding of relay 443 is also connected. Relay 562 and the left hand lowresistance winding of relay 564 are brought into connection with brush57 2 over sequence switch contact 554. Sequence switch 550 is nowenergized in a circuit over its contact 557 bottom and front contact ofrelay 562. Sequence switch 550 starts from position 6 and moves overposition 8 into position 9 in which the fundamental circuit is extendedat sequence switch contacts 553 top and 559 top to the final selector.Test brush 572 is now connected over sequence switch contact 566,resistance 570 and right hand front contact of relay 543 to ground.Relay 562 is con-' nected in parallel to resistance 570 over contact 545top of the sequence switch, whereby relay 562 is maintained energized.

Sequence switch 350 remains in position 10 until the dialling of thefourth figure is completed at the subscribers station and: sequenceswitch 320 leaves position 11. Sequence switch 350 is then. energized ina circuit over contact 352 top and contact 346 bottom of sequence switch320. Sequence switch 350 starts from position 10 and moves into position11 in which the fundamental circuit is again closed at contact 358bottom of sequence switch 356. Relay of the register set and relay 452of the final selector are now energized. The sequence switch 450 isenergized in a circuit over contact 446 top and front contact of relay452. Sequence switch 450 starts from position 1 and moves into position2 in which the magnet 448 of the trip spindle is energized in a circuitover sequence switch contact 447 bottom and front contact of relay 452.The trip spindle rotates and provides at contact 455 top over sequenceswitch contact 449 bottom shortcircuitings around the winding of relay355. The tens register 130 is now restored to position '0 under thecontrol of relay 355 in a circuit over contact 132 of register 130,contact 367 top of sequence switch 350 and back contact of relay 359.When register 130 reaches position 0 relay 357 and sequence switch 350are energized in a circuit including sequence switch contact 370 top,contact 134 of register 130 and sequence switch contact 367 top. Thefundamental circuit is opened and sequence switch 350 starts fromposit-ion 11 and moves intoposition 12. When contact 455 of the tripspindle is also opened relay 452 at the final selector is de-energized,sequence switch 450 is energized in a circuit over contact 456 top andback contacts of relays 462 and 452. Sequence switch 450 starts fromposition 2'and moves into position 3.

Sequence switch 350 remains in position 12 until the dialling of thelast figure is completed at the calling station and sequence switch 320leaves position 13. A circuit is then established over contact 363 topof sequence switch 350 and contact 330 of sequence switch 320. Sequenceswitch 350 starts'from position 12 and moves into position 14 in whichthe fundamental circuitis closed at the register set at sequence switchcontact 358 top. Relay 452 is again energized and provides a circuit forthe energization .of sequence switch 450 over contact 446 and frontcontact of relay 452. Sequence switch 450 starts from position 3 andmoves into'position 4 in which the power magnet 461 is energized in acircuit over sequence switch con-tact 446 bottom and front contact ofrelay 452. The brush carriage of the final selector rotates, producingover contact 457 top and contact 449 of the sequence switch shortcircuitings around the winding of relay 355. Under the control of relay355 the units register 140 is now restored to position 0 in a circuitover contact 142 and sequence switch contact 367 bottom. When register140 is in postion 0 relay 357 and sequence switch 350 are energized onthe following de-energization of relay 355 in a circuit over sequenceswitch contact 370 top, contact 144 of register 140, back contact ofrelay 374, contact 143 of register 140 and sequence switch contact 367.Sequence switch 350 starts from position 14, 7

1Vhen sequence switch 350 moves over :poe sition 14 a circuitisestablished for the energization of the left hand winding of relay 339over contact 327 bottom of sequence switch 320, contact 368 bottom ofsequence switch 350, left hand back contact of relay 378 and contact 369bottom of sequence switch 350. Relay 339opens at its back con tact thecircuit of relay 222 of the cord and provides over its front contact aholding circuit for its left hand winding. The de energization of relay222 causes sequence switch 220 to start from position 9 and to move intoposition 10 whereby the stepping relay 325 of the register set isdisconnected from the calling line which is again brought intoconnection with relay 231 and retardation coil 237. Sequence switch 220is in position 10 energized in a circuit over back contact of relay 2'62and the sequence switch moves into position 11.

The de-energization of relay 325 provides a circuit for the energizationof sequence switch 320 over contact 348 bottom and back contacts ofrelays 325 and 323. Sequence switch 320 starts from position 15 andmoves into position 16 in which relay 339 is tie-energized and a circuitis established for the energization of sequence switch 350 over contact340 bottom of sequence switch 320. Sequence switch 350 testing thepositions of the registers moves over positions 16, 17 and 18 intoposition 1. The cir cuit for moving sequence switch 350 out of position16 leads from battery through the winding of the magnet of said sequenceswitch, contact 363 closed in position 16, cont-act 104, contact 364closed in position 16, contact 114, contact 361 closed in position 16,contact 124, contact 366 closed in position 16, lower contact 340 ofsequence switch 320, back contact and armature of relay 339 to ground.Sequence switch 350 moves into position 17 where the following circuitis closed, provided register 130 has reached its normal position:battery, through the winding'of sequence switch 350, upper contact 370,contact 134,contact 367 closed in position 17, and thence to ground atthe back contact and armature of relay 339. Sequence switch 350 moves inposition 18 and the following circuit is closed to advance the same intoposition 1, provided the units register 140 has reached its normalposition: battery, through the winding of sequence switch 350, uppercontact 370, contact 144,

back contact and armature of relay 374, contact 143, lower contact 367closed in position 18 to ground, as described, at the back contact andarmature of relay 339. A circuit is then established for theenergization of sequence switch 320 over contact 326 top and contact 369top of sequence switch 350. Sequence switch 320 starts from position 16.In position 18 the energization of Sequence switch 320 is maintainedover con tact 348 bottom and back contact of relay 325. Sequence switch320 moves into position 1 and the register is free for other calls.

When at the final selector contact 457 of the brush carriage is openedrelay 452 is deenergized and causes sequence switch 450 to start fromposition 4 and to move into position 10. Sequence switch 450 firstadvances from position 4 into position 6 by means of acircuit frombattery through the winding of said sequence switch upper contact 456,back contact and armature of relay 462, and back contact and armature ofrelay 452 to ground. In position 6 of sequence switch 450, relay 452 isenergized in a circuit from battery through the winding of said relay,lower contact 459 to ground. Relay 452 attracts its armature and acircuit is established from battery through the winding of sequenceswitch 450, upper contact 446, front contact and armature of relay 452to ground, whereby the said sequence switch advances out of position 6and into position 10. As soon as contact 441 of sequence switch 450 isopened relay 562 at the third group selector is de-energized andsequence switch 550 is energized in a circuit over contact 547 top andback contact of relay 562. Sequence switch 550 starts from position 9and moves over position 11. into position 12. Contact 541 is then openedand relay 532 at the second group selector is tie-energized causing theenergization of sequence switch 520 in a circuit over contact 515 topand back contact of relay 532. Sequence switch 520 starts from position6 and moves into position 9 in which relay 523 is again brought intoconnection with the trunk line over sequence switch contacts 506 top and505 bottom, and relay 525 and retardation coil 526 are connected oversequence switch contacts 51'. and 518 with the final selector. The timefor the energization of relay 339 at the register set and thede-energization of relay 222 at the cord is so selected that sequenceswitch 220 advances into position 10 and brings relay 262 and.retardation coil 257 in bridge to the trunk line after the sequenceswitch 450 of the final selector has left position 4 and contact 444bottom is opened, while relay 231 of the cord in position 10 of sequenceswitch 220 is energized over the calling subscriber line before sequenceswitch 520 at the second group selector reaches position 9 so that relay523 is energized over the trunk line and front contact of relay 231.

When sequence switch 450 passes position 7 terminal 470 of the alledline is tested and if found free relay 454 is energized in a circuitincluding the cut-off relay of the called. line and sequence switchcontact 459 top. Relay 462 and the low resistance winding of relay 454are brought over the front contact of relay 464 in parallel to the highresistance winding of said relay and terminal 470 is made busy. Relay462 when energized provides a circuit for the energization of sequenceswitch 450 over contact 453 top and front contact of relay 462. Sequenceswitch 450 moves over positions 10 and 11 into position 12 in which analternating ringing current is immediately sent to the station of thewanted line. Relay 452 is brought into connection with the commoninterrupter 459 which when closed causes the energization of relay 452whereby sequence switch 450 is energized in a circuit over the frontcontact of this relay and moves into position 13. The circuit forenergizing relay may be traced from battery through the winding of saidrelay, lower contact 490, interrupter 469 to ground. Relay 452 is nowconnected, sequence switch 450 being in position 18, with a furthercommon interrupter 472. The curcuit including interrupter 47 2 istraceable from battery through the winding of relay 452, contact 491 toground at interrupter 47 2. The two interrupters 469 and 4'72 arecontinuously operated and are arranged to close the circuit to ground atpredetermined time intervals so that sequence switch 450 when reachingposition 12 is brought after the lapse of a few seconds over positions12 and 13 into position 14 in which the direct connection of the ringingcurrent supply is removed and the connection of the subscribers linewith the ringing source of current is maintained over a commoninterrupter 474, which at selected intervals connects in succession thecircuit either to the source of ringing current or to ground. Thepermanent ringing circuit may be traced from the ringing source atmachine 474, lower contact 473 thence to the lower tall:- ing conductorof the line and returning by way of the upper talking conductor to thelower contact 457, winding of relay 460 to battery and ground. Duringthe time sequence switch 450 is in position 12 to 14 the primary windingof the tone coil 477 is connected to common interrupter, and thesecondary winding of this coil is connected in bridge to the line andthe calling subscriber perceives an indication that the ringing of thecalled party is proceeding. As soon as the receiver is lifted from thehook at the wanted station, ringing relay 460 is energized and causesover its front contact the cnergization of sequence switch 450 whichstarts from position 14 and moves into position 15 in which a throughconnection of the called suhscrili er line is made to the transmittercurrent supply bridge at the second roup selector. Relay is thereby ene"zed and provides a shunt around the high resistance winding of relay523. Relay :2 at the cord is thereby enerzed and provides over its frontcontact a for the encrgization of sequence circuit .ister 110.

switch 220 which starts from and moves into position 12.

The translation from the decimal number system of the wanted subscriberline to the system of the switches is so made that if the thousandsregister 110 when under the control of the dial is arrested in an oddposition relay 360 is energized in a circuit over contact 116 ofregister 110 and contact 379 bottom of sequence switch 350 in position5. Relay 360 provides a holding circuit for its winding over its righthand front contact and sequence switch contact 3 2 top, while position11 7 over the left hand contact of relay 360 the circuit for therestoration of register 110 is so modified that in position 6 ofsequence switch 350 the circuit for the register is closed over contact113 and the register is restored to position 9 instead of to position 0,after which sequence switch 350 is energized in a circuit over contact112 of register 110, left hand front contact of relay 360 and contact115 of register 110. The trip spindle of the second group selector makestherefore the same number of steps whether the register 110 has beenarrested in an even position or in the following odd position. Aftersequence switch 350 leaves position 6 relay 360 is ole-energized andwhen in position 9 of sequence switch 350 the hundreds register 120 isrestored to position 0 the circuit is first extended over contact 124 ofregister 120, contact 361 bottom of sequence switch 350, contact 112 ofregister 110 and left hand back contact of relay 360 to reg- The tripspindle of the third group selectors makes therefore, an addi tionalstep.

If the hundreds register 120 has been advanced under the control of thedial into an odd position relays 373 and 374 are energized in a circuitover contact 375 of sequence switch 350 and contact 126 of register 120in position 8 of this sequence switch, whereby relay 373 provides alocking circuit over its front contact and contact 372 bottom ofsequence switch 350. During the time sequence switch 350 moves overposition 8 the register 120 is energized in a circuit over contact 122,contact 366 top of sequence switch 350 and contact 126 of register 120.The register 120 makes an additional step and takes the same position asif the next higher even figure has been dialled. The trip spindle of athird selector takes, therefore, the same position disregarding whetherthe third figure of the wanted number was even or odd, and aftersequence switch 350 leaves position 12, relays 373 and 374 aremaintained energized over contact 146 of register 140 and control thetranslation of the units impulses for the final selector causing theadvance of the brush carriage to the second half of the terminal row.

When the brush carriage of a final selector moves between the first andsecond half of the terminal arc, the short circuiting contact 457 of thebrush carriage is in the well known manner closed for a comparativelylong time and, if the wanted number corresponds to the first terminal inthe second half of the terminal arc, the long closure of contact 457delays the starting of sequence switch 450 and the opening of contact444. In order that sequence switch 220 of the cord shall notmove intoposition 10 before contact 444 of sequence switch 450 is opened at thefinal selector the circuit at the register is so arranged that if theterminal of the wanted number is the first in the second half of theterminal arc of a final selector the energization of relay 339 at theregister set and in consequence the deenergization of relay 222 of thecord is correspondingly delayed. The first terminal of the second halfof the terminal are corresponds to an odd position of register 120 andposition 0 of register 140. If, therefore, relay 373 has been energizedon an odd po sition of register 120 and if register 140 is arrested inposition 0 a circuit is closed in position 13 of sequence switch 350 forthe energization of relay 378 over contact 145 of register 140, contact375 bottom of sequence switch 350, front contact of relay 373, contact146 of register 140 and contact 369 bottom of sequence switch 350. Relay378 once energized maintains its'energization over its left hand frontcontact and sequence switch contact 369. When after the completion ofthe selection sequence switch 350 reaches position 14 the circuit forrelay 339 is maintained open at the left hand back contact of relay 378,and the circuit is closed in position 15 of sequence switch 350 oversequence top, front contact of relay 378 and sequence switch contact369.

When after the conversation relay 231 is de-energized, sequence switch220 starts from position 12 and moves over position 13 into position 17,the metering battery 259 is connected to terminal 238 during the timesequence switch 220 passes over positions 14 to 16, whereby the meter208 at the calling subscriber line is operated. In position 17 ofsequence switch 220 the power magnet 241 is energized and the brushcarriage rotates until its home contact 269 is reached, whereby relay232 is energized in a circuit over contact 269. The brush carriage isarrested, sequence switch 220 starts from position 17 and moves intoposition 18 in which the sequence switch remains until the second cordof the pair becomes engaged with a call.

Relay 523 at the incoming end of the twowire trunk is de-energ'zed assoon as front contact of relay 231 is opened in the outgoing exchange.Relay 522 is thereby enerswitch contact 368 gized in a circuit oversequence switch contact 504 bottom and back contact of relay 523.Sequence switch 520 is energized in a circuit over contact 514 bottomand front contact of relay 522. Sequence switch 520 starts from position9 and moves into pos1- tion 11 in which the power magnet 531 isenergized and the brush carriage is restored to its position of rest,whereby after its home contact 539 is closed relay 532 is energized in acircuit over contact 539, sequence switch contact 516 and holding magnet535. The brush carriage is arrested, and sequence switch 520 isenergized in a circuit over front contact of relay 532. Sequence sw.tch520 startsfrom position 11 and moves into position 1. hen contact 513 ofsequence switch 520 is opened relay 543 at the third group selector isde-energized and causes the energization of sequence switch 550 in acircuit over contact 544 top and right hand back contact of relay 543.Sequence switch 550 starts from position 12 and moves into position 14in which the power magnet 561 is energized and the brush carriage isrestored to its position of rest, whereby after the home contact 569 isclosed relay 562 is energized in a circuit over contact 569, sequenceswitch contact 560 top and holding magnet 565. The brush carriage isarrested, and sequence switch 550 is energized in a circuit over itscontact 557 and front contact of relay 562. Sequence switch 550 startsfrom position 14 and moves into position 1.

When relay 543 opens its right hand front contact, relay 443 of thefinal selector is deenergized and provides a circuit for theenergization of sequence switch 450 over contact 458 top and right handback contact of relay 443. Sequence switch 450 starts from position 15and moves into position 17 in which relay 460 is brought into connectionwith the called line over sequence switch contact 466 bottom, thecircuit also including sequence switch contacts 467 and 445. Relay 462and the cut-off relay of the called line are held energized in a circuitover contact 478 of sequence switch 450 independent from the frontcontact of relay 443. If the called subscriber has not restored hisreceiver relay 460 becomes energized and provides over its front contactand over sequence switch contact 440 bottom a circuit for theenergization of relay 443. Sequence switch 450 is held in position 17.The circuit is established over back contact of relay 452, front contactof relay 462 and sequence switch contact 453 bottom to a common timealarm, which after the lapse of a given time provides a signal in theexchange. After the called subscriber has also restored his receiver,relay 460 and in consequence relay 443 are deenergized, sequence switch450 starts from position 17 and moves into position 18, in

which the brush carriage of the final is restored to its position ofrest. Sequence switch 450 moves then from position 18 into position 1.

The outgoing end of the two-wire trunk in the first exchange ismaintained busy until the second group selector at the incoming end ofthe trunk line is restored to its position of rest and its sequenceswitch 520 is in position 1. When the cord is released and sequenceswitch 220 opens its contact 228 relay 502 is de-energized. A circuit isthen prepared over right hand back contact of relay 502, right handfront contact of relay 501, winding of relay 503 and the common wire529, and as soon as sequence switch 520 in the distant exchange reachesposition 1 the high resistance winding of relay 503 is energized in acircuit over wire 536 of the trunk line, contact 504 of sequence switch520 and relay 522. Relay 503 disconnects on its back contact the righthand holding winding of relay 501, which when de-energized disconnectsat its right hand front contact relay 503 and connects at its left handback contact resistance 500 to battery so that the trunk line is againmade free.

If the called subscriber is the first to restore his receiver on thehook, relay 525 at the second group selector is de-energized and opensthe shunt around the high resistance winding of relay 523. Relay 262 atthe cord is thereby de-energized and sequence switch 220 is energized ina circuit over back contact of relay 262. Sequence switch 220 startsfrom position 12 and moves into position 13. The brushes of the firstgroup selector are thereby disconnected. The second group selector andthe final selector are released, while the sequence switch of the cordremains in position 13 and the calling line is held busy until thecalling subscriber restores his receiver and relay 231 is de-energized.The cord is then released and the meter-208 of the subscriber line isoperated.

If the wanted line has been found busy and the test relays 464 and 462have notbeen energized when sequence switch 450 of the final selectormoves over position 7, sequence switch 450 is arrested in position 10.The secondary winding of the busy tone coil 477 is thereby brought inbridge to theline and the calling subscriber receives a busy tone. Whenthe subscriber restores his receiver and relay 231 is de-energizedacircuit is established for the energizationof the left hand winding ofmetering-hindering relay 224. Belay 224 disconnects at itsleft hand backcontact the circuit for relays .235, 213 and 207, while over the lefthand front contact of relay 24 a holding circuit is provided for itsleft hand winding. right hand front contact of relay 224 and its righthand low resistance winding a circuit is established for theenergization of @ver the I sequence switch 220 which starts fromposition 11 and moves over positions 12 and 13 into position 17. Thesecond and third group selectors are released as has been described.Relay 443 at the final selector is de-energized, sequence switch 450starts from position 10 and moves into position 11 in which the brushesare restored to their position of rest, whereby after contact 457 bottomis closed relay 452 is energized. Sequence switch 450 starts fromposition 11 and moves into position' 1.

Since sequence switch 220 is held in position 11 whether the wanted lineis found busy or a ringing current is sent to the Wanted station, relay224 is energized if the calling subscriber gives up the connectionbefore the called subscriber has answered. The release proceeds, withoutmetering, also if the sequence switch of the final selector is in itsringing position and the called subscriber does not answer.

A connection can be released before the selection is completed if thecalling subscriber restores his receiver on the hook, whereby if thecall is given up during the dialling and relay 325 remains de-energizedfor a longer time than on the last opening at the dial, relay 339becomes energized when sequence switch 320 passes over one of itspositions 5, 7 10 or 12%. If the release is started and relay 325 isde-energized after the dialling is completed but before the selectorshave been set up under the control of the register set, thede-energization of relay 325 causes the energization of sequence switch320 in the circuit over contact 348, sequence switch 320 starts fromposition 15 and opens contact 340. When rela 222 of the cord isole-energized, sequence switch 220 starts and relay 224 is energized assoon as sequence switch 220 reaches position 8 or position 11. If relay224 is energized in position 8 of sequence switch 220 the sequenceswitch is arrested and the brush carriage is first restored to itsposition of rest, after which sequence switch 220 completes itsrotation. Sequence switch 320 is held in position 16 until the registersare restored to their position 0. The back contact of relay 359 isconnected over contact 340 bottomof sequence switch 320 and back contactof relay 339 direct to ground, while relay 359 is maintained energizedover back contact of relay 355.

. When a release is started and relay 222 in the cord is de-energized ata stage in which sequence switch 220 is in position 7 the brush carriageis restored to its position of rest in position 8 of the sequenceswitch, during which relay 222 remains connected over sequence switchcontact 246 top to wire'293. If the sequence switch 320 reaches position18 before contact 246 of sequence switch 220 is opened, a circuit isestablished for the energization of relay 339 over wire 293, contact 322top of sequence switch 320, right hand windingof relay 339, contact3430f sequence switch 320 and back contact of relay 355. The left handwinding of stepping relay 325 is then energized in a circuit oversequence switch contact 327 top and front contact of relay 339. Sequenceswitch 320 is held in position 18 until relay 339 and in consequencerelay 325 are de-energized.

When the release begins and the fundamental circuit is opened at themoment relay 522 of the second group selector was energized and sequenceswitch 520 has started from position 1 but trip spindle magnet 528 wasnot energized and its contact 510 bottom was not closed, the sequenceswitch 520 starts from position 2 and relay 522 remaining de-energizedin position 3 of the sequence switch, the circuit is maintained overback contact of relay 522 and the sequence switch moves over position 3into position 5. Relay is energized in a circuit over the home contact539 of the brush carriage and sequence switch 520'moves over position 5into position 6 in which the sequence switch is energized in a circuitover the back contact of relay 532. Sequence switch 520 moves intoposition 11 in which relay 532 is again energized in a circuit overcontact Sequence switch 520 then completes its rotation, after which theoutgoing end of the trunk line is given free.

if a release is started during the time the second group selectorsearches for a free third selector, the brush carriage continues torotate until the terminals of a free third selector are reached andrelays 534 and 532 are energized; after which sequence switch 520movesinto position 6. The energization of relay 543 at the third groupselector causes sequence switch 550 to start from position 1 and to moveinto position 2. Since the outgoing end of the two-wire trunk line iskept busy in the first exchange the fundamental circuit cannot be closedover the third group selector. In order that the second group selectormay not be held permanently out of service the circuit is brought underthe control of a common timing arrangement such as shown in Fig. .8 andthe switches are released after the lapse of a suflicient time. For thispurpose in position 2 of sequence switch 550 relay 562 is energized in acircuit over back contact of relay 564, sequence switch contact 545bottom and holding magnet 565. The right hand winding of test relay 564is connected over sequence switch contact 546 bottom,-

wire 591 to contact 582 of sequence switch 580. Whenever the sequenceswitch of a second group selector at the incoming end of a two-wiretrunk is in position 6 a circuit is closed for relay 584 of the commontiming arrangement over conductor and con tact 519 of sequence switch520 to a common interrupter 589, whereby each time the commoninterrupter is closed relay 584 is energized. Sequence switch 580 isadvanced one step when relay 584 is energized and another step whenrelay 584 is de-energized, since sequence switch 580 is energized eitherover front contact of relay 584 and sequence switch contact 583 bottomor over back contact of relay 584 and sequence switch contact 588 top.Sequence switch 580 is advanced, therefore, at given time intervals fromthe position in, which the sequence switch happens to stay, and whenpassing position 9 a circuit. is established for the energization ofrelay 564 of a third group selector, the sequence switch of which is inposition 2. The energization of relay 564 causes the opening of thecircuit of relay which is thereby tie-energized. Sequence switch 550 isthen energized in a circuit over contact 547 top and back contact ofrelay 562. Sequence switch 550starts from position 2 and moves intoposition 4. Contact 582 of sequence switch 580 is opened and relay 564is de-energized causing the deenergization of relay 562 at the thirdgroup selector before sequence switch 550 reaches position 4. Sequenceswitch 580 continues its movement under the control of relay 584 andafter passing position 9 a second time contact 582 is again closed andrelay 56-1!- is again energized. Relay 562 is de-energized so thatsequence switch 550 starts from position 4'and moves into position 5.

The fundamental circuit of the third group selector can also remain openat the register set if the subscriber for some reason delays thediallingof the third figure. The time sequence switch a cycle of operation istherefore so selected that ample time is provided for any delay at thecalling station and only if the calling subscriber holds up thecompletion of the dialling for any unreasonably long time is sequenceswitch 550 on the third group selector advanced to a position on whichthe fundamental circuit is opened. The time sequence switch 580 needsfor the completion of a cycle of operation can be shortened byconnecting its contact 585 to ground, and for lengthening the time of acycle relays 586 and 587 are provided in the circuit, whereby the wiringis so changed that front contact of relay 584 is disconnected fromcontact 588 bottom and connected to the armature of relay 587. Themanner in which the front contact of relay 584 is connected to thearmature of relay 587 for the purpose of increasing the time interval isillustrated in Fig. 10. When relay 584 closes its front contact relay586 is energized over front contact of relay 584 and back contact ofrelay 587. Relay 586 provides a locking circuit for its winding over 580needs to complete its front contact, the winding of relay 587 andsequence switch contact 588. Relay 587 remains short-circuited as longas relay 584 is energized. After the front contact of relay 584 isopened relay 587 is energized and connects the front contact of relay584 to sequence switch contact 588 bottom. When relay 584 is againenergized sequence switch 580 is energized in a circuit over its contact588 bottom and front contacts of relays 587 and 584. Sequence switch 580starts from position 1 and moves into position 2. Contact 588 is openedand relay 587 is de-energized. After relay 584 closes its back contactsequence switch 580 moves from position 2 into position 8 in whichcontact 588 is again closed. The interrupter 589 must therefore beclosed twice in order that sequence switch 580 can move from position 1into its position 3 and so on.

lVhen sequence switch 550 of the third group selector is in position 5and the fundamental circuit is not closed relay 552 remainstie-energized and sequence switch 550 moves into position 6. Contact 555bottom of the trip spindle being opened, relay 522 remains de-energizedand sequence switch 550 moves from position 6 into po sition 8 in whichrelay 562 is energized in a circuit over the home contact 569 of thebrush carriage. Sequence switch 550 moves over position 8 into position9. Relay 562 is thereby de-energized and sequence switch 550 moves overpositions 9 and 11 into position 12 in which contact 541 is opened.

l/Vhen a release is started at the time a third group selector issearching for a free final selector the brush carriage of the thirdgroup selector continues to rotate until the terminals of a free finalselector are reached. Relay 564 is thereby energized over contact 546top of sequence switch 550 in position 6 as has been described, andsequence switch 550 starts from position 6 and moves over position 8into position 9 in which terminal 57 2 is made busy over sequence switchcontact 566, resistance 570 and front contact of relay 548. Relay 562 isenergized in a parallel circuit to resistance 572 over back contact ofrelay 564, sequence switch contact 545 top, terminal 572 and resistance442 of the final selector. The right hand winding of relay 564' is againconnected over contact 546 of sequence switch 550 to wire 591, and whensequence switch 580 passes over position 9 relay 564 is energized andrelay 562 is (Il6-81161gl26d. Sequence switch 550 is then energized andmoves from position 9 into position 11. During the time relay 562 isdisconnected terminal 572 is maintained busy over resistance 570. Aftersequence switch 580 passes position 9 a second time, relay 564 isenergized. Sequence switch 550 leaves position 11 and moves into llH (iii position 12. Resistance 542 is disconnected at contact 541 of sequenceswitch 550 so that relay 532 at the second group selector is deenergize'd and sequence switch 520' leaves position 6 and completes itsrotation.

l Vhen the release is started and the fundamental circuit'is opened atthe tinjie relay 452 of the final selector has already been energizedand sequence switch 450 is in position 2, the sequence switch moves intoposition 3 wliere it is held until the switch of the third groupselector under the control of sequence switch 550 leaves positions 9 and11. whereby the second group selector is released, and after relay 543is dc-energized the circuit for relay 443 is opened. Sequence switch 450is energized in a circuit over back contact 0-1 relay 443.

\Vhen the release is started at the time sequence switch 450 of thefinal selector is in position 4 the deenergization of relay "1 52 causessequence switch 450 to start from position 4;. After contact 441 isopened relay 562 at the third group selector is de energized, sequenceswitch 550 moves over position 11. Relay 532 at the second groupselector is de energized and sequence switch 520 starts from position 6and moves over position 9, whereby relay 543 and in consequence relay l13 are tie-energized before sequence switch 450 reaches position ll.Relay 462 can thereby not be energized at the terminal of a subscriberline on which the brushes of the final selector happen to stay, thebrush carriage is first restored to its position of res after whichsequence switch 450 completes its rotation.

The automatic release of a second group selector on the incoming end ofa two-wire trunk line after the lapse of a reasonable time together withthe arrangement to hold the outgoing end oil? the trunk line busy untilthe sequence switch of the group selector returns into its position ofrest allows each register to control immediately the correspondingselector after the series of impulses are completed on the dial for thisregister. On an average the setting up of a selector and its connectionwith a tree trunk line to a following selector is shorter than the timethe subscriber uses for dialling the succeeding figure of the wantednumber. Counting from the moment the subscriber removes the receiverfrom the hook, the time required to complete a connection is, therefore,appreciably reduced when each register immediately controls thecorresponding selector. It would sutlice to connect the second groupselector on the incoming end of a two-wire trunk with the common delayarrangement for the automatic release, in which case spare positions onsequence switch 520 could be provided so as to advance it from position6, but it sequence was found more practical to control the sequenceswitch of the succeeding selector from the common delaying arrangement.

In a system in which the impulses from the dial can be accumulated inthe register set and the selectors are enabled to continue searching itall succeeding selectors are busy until a trunk line becomes free, thenumber of trunk lines and selectors in a given group can be in practiceappreciably reduced it permitting in exceptional cases during the busyhour the delaying of a connection until a trunk line has become free. Ifall final selectors to a given group of subscribers were busy and theprogress of a selection was delayed because the third group se lectorcontinues to rotate and to search for a trunk line, and should theconnection of the timing arrangement for an automatic release beconnected direct to the second group selector, the time a call is sokept waiting would have to be added to the time a subscriber may suspendthe completion of dialling. Since it may happen that a sequence switchoi a group selector arrives'in the position where it is connected withthe timing arrangement at the moment after the common circuit foradvancing the sequence switch has been opened, the automatic release ofthe sequence switch will then take a still longer time and the switcheswould be held after a 'n'emature release an unreasonably long time. 1

When a figure is'erroneously dialled which causes the advance of thegroup selector on the incoming end of a two-wire trunk to a dead level;the group selector obtains a connection with a trunk'line such as'shown'in Fig. 9. Test relay 534s of the group selector is therebyenergized in a circuit over terminal 692, resistance 696' and backcontacts of relays 699 and 697, and also over the windings of relays69'3and-694 connected in parallel to resistance 696. Relay 693 whenenergized connects the windings of relay 695 which are diil'erenti'a'llywound and the interrupter 690 in bridge to the trunk line. Each time thefundamental circuit at the register set containing rela 1 355 is-clo'sedthe interrupter 690 causes energizations of relay 355 and the registersare restored in succession, while relay 695 remains de-energized. Afterthe restoration of the registers is completed relay 222 of the cord isdeenergized and the sequence switch 220 advances into position 10. Acircuit is established over the left hand winding of relay 695 one wireof the trunk line and relay 262 of the cord. A second circuit isprepared over the right handwinding of relay 695 and retardation coil257 of the cord. When the interrupter 690 is opened relay 695 isenergized and provides on its front contact a circuit for the left handwinding of relay 697 which relay when energized opens its back contactand brings its right hand high resistance'winding in the circuit ofterminal 692. Relay 693 line and relay 532 at the second group selectorare thereby tie-energized. Sequence switch 520 leaves position 6 andmoves into position 9. A circuit for the lamp 698 is established overthe front contact of relay 697. An operator in depressing key 680communicates with the calling subscriber. Relay 699 is therebyenergized, lamp 698 is disconnected at the right hand back contact ofthis relay and a holding circuit is established for the winding of relay699 over its right hand front contact and front contactof relay 697. Atthe left hand back contact of relay 699 is the shunt around the windingof relay 697 maintained open. After the calling subscriber restores hisreceiver on the hook and the switches are released, terminal 692 appearsengaged until the key 680 is restored and relay 699 is de-energized. Onthe other hand if key 680 is restored be fore the switches are releasedrelay 699 is maintained energized until relay 697 is deenergized so thatthe circuit for the lamp 698 is held open.

If the subscriber has noticed the error and gives up the call theregister set and the cord are released as has been described. Relay 697can, therefore, not become energized, relay 532 at the second groupselector remains energized and sequence switch 520 is held in position6. In order to release automatically the second group selector anarrangement is 'made whereby relay 694 provides over its right handfront contact a connection for relay 684 with common wire 691 which isconnected with the common delaying arrangement shown-in Fig. 8. Whensequence switch 580 passes over its position 9 relay 684 is energizedand provides over its front contact and back contact of relay 687 acircuit for the energization of relay 686. After relay 684 istie-energized relay 687 is energized in a circuit over the winding andfront contact of relay686 and the right hand front contact of relay 694.When sequence switch 580 passes position 9 a sec- 0nd time and relay 684is again energized a circuit is established for the energization ofrelay 697 over the front contacts of relays 687 and 684. Relay 532 atthe second group selector is then de-energized and sequence switch 520leaves its position 6.

For a forced release of a local connection from the tollboard over theswitching section the test terminal of the subscriber line is for ashort time interval connected direct to ground and then made busy. Thesubscriber wanted for a toll connection can be either the called or thecalling party in a local connection. If the wanted subscriber is thecalling party terminal 218 is connected to ground. Relay'235 at thecordis de-enat the trunk ergized and provides at its right hand backcontact a circuit for the energization of relay 224 over contact 243 topof sequence switch 220 and retardation coil 237. The sequence switch 220is started and the release of the cord, the second and third groupselectors, is completed as has been described. The sequence switch ofthe final selector is thereby held in its position 17 until the calledsubscriber restores his receiver on the hook. If the forced releasehappens at the time sequence switch 220 is in positions 5 to 9 and thecord is connected with the register set, the energization of relay 224takes lace in a circuit over sequence switch contact 243 bottom, wire295 and one winding of stepping relay 325. When sequence switch 220leaves position 9 the stepping relay 325 is de-energized and theregister set is released.

When the subscriber is the called party in the connection and terminal470 is con nected at the switching section to ground. relays 462 and 464are de-energized and cannot become again energized since terminal 470 isimmediately made busy at the switching section. Sequence switch 450-isthen energized in a circuit over its contact 456 top and back contact ofrelay 462. As

soon as the through connection with the called line is opened atsequence switch contact 473 relay 525 of the second group selector, istie-energized and in opening the shunt around the high resistancewinding of relay 523 causes the de-energization of re-- lay 262 at thecord so that sequence switch 220 startsfrom position 12 and moves intoposition 13, after which, the second; third and final selectors arereleased. The sequence switch of the cord is held in position 13 untilrelay 231 is ole-energized.

For obtaining a connection over the first group selector with a distantmanual board the subscriber dials two fi ures. When register 100 isadvanced under the control of the dial into positions 1 or 0 and whensequence switch 350 is started from position 1, a circuit is establishedin position 2 of the sequence switch for the energization of relay 378over contact 105 of register'lOO and sequence switch contact 379 top.Relay 37 8 provides over its left hand front contact a holding circuitfor its winding traceable from battery through the winding, frontcontact. and left-hand armature of said relay, lower contact 369 toground. In position 3 of sequence switch 350 the trip spindle of thefirst group selector is set up according to the position of register100. The brush carriage of the first group selector obtains then aconnection with a free trunk line. After the second figure isdialled andsequence switch 350 advances into position 6 a circuit is establishedfor the energization of relay 339 over one wire of the trunk

